We should also know that 'greed' has little to do with the environmental crisis. The two main causes are population pressures, especially the pressures of large metropolitan populations, and the desire—a highly commendable(praiseworthy)one—to bring a decent living at the lowest possible cost to the largest possible number of people. The environmental crisis is the result of success—success in cutting down the mortality (死亡率)of infants (which has given us the population explosion), success in raising farm output sufficiently to prevent mass famine (which has given us contaminati9n by pesticides and chemical fertilizers), success in getting people out of the houses of the 19th-century city and into the teenager and privacy of the single-family home in the suburbs(which has given us urban sprawl and traffic jams). The environmental crisis, in other words, is largely the result of doing too much of the right sort of thing. To overcome the problems that success always creates, one must build on it. But where to start? cleaning up the environment requires determined, sustained effort with clear targets and deadlines. It requires, above all, concentration of effort UP to now we have tried to do a little bit of everything—when what eve ought to do first is draw up a list of priorities. This passage assumed the desirability of______.